I'm hoping someone can offer some help, I've been working on this for
some time now
I'm running STATA 8.2 SE and have a large dataset (>90,000 rows of data
with about 12,000 unique record numbers, multiple observations for the
same individual).
I'm trying to calculate a "time out of range" for each patient (i.e. the
proportion of each patients observation time that is predicted to be
greater than 140 assuming a linearly interpolated slope of acutally
measured blood pressures--not simply the proportion of blood pressure
readings that is > than my threshold). I have 3 variables: MRN (medical
record number), Visit_date, bp_systolic
I've run into a problem due to the size of my data set, specifically
that I have too many levels. Here is my code
encode mrn, gen (pt)
sort pt visit_date
drop if bp_systolic==.
by pt:gen obstime =visit_date[_n+1]-visit_date
by pt:gen sys_diff=bp_systolic[_n+1]-bp_systolic
by pt:gen slope=sys_diff/obstime
by pt:gen predict=(140-bp_systolic)/slope if bp_systolic<140 &
bp_systolic[_n+1]>=140
by pt:gen date140=visit_date + predict
by pt:gen predict2=floor([140-bp_systolic]/slope) if bp_systolic>=140 &
bp_systolic[_n+1]<140
by pt:gen date140down=visit_date[_n-1] - predict2
by pt:gen out_range=obstime if bp_systolic>=140 & bp_systolic[_n+1]>=140
by pt: replace out_range=visit_date[_n+1]- date140 if bp_systolic<140 &
bp_systolic[_n+1]>=140
by pt: replace out_range=obstime- predict2 if bp_systolic>=140 &
bp_systolic[_n+1] <140
gen time=.
levels pt, local(levels)
quietly foreach l of local levels {
sum obstime if pt==`l'
local total=r(sum)
replace time=`total' if pt==`l'
}
gen time_out=.
quietly foreach l of local levels {
sum out_range if pt==`l'
local total =r(sum)
replace time_out=`total' if pt==`l'
}
gen time_o_r=(time_out/time)
local threshold = 140
gen proportion=.
levels pt, local(levels)
quietly foreach l of local levels {
count if pt == `l' & bp_systolic !=.
local total =r(N)
count if bp_systolic >= `threshold' & bp_systolic !=. & pt == `l'
replace proportion = r(N)/`total' if pt == `l'
}
Any suggestions for using a different set of programming statements???
Thanks,
AO
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